This project comprises three studies of oral cancer and oral mucosal lesions. In one study persons with white or red oral mucosal lesions seen at six Department of Veterans Administration (VA) undergo a biopsy of all suspect oral lesions and provide oral epithelial cells and information about tobacco and alcohol intake. They are re-examined and provide oral epithelial cells periodically. The purpose of this study is to identify determinants, such as genotypes that are involved in tobacco and alcohol metabolism, of microsatellite instability and DNA adduct formation. This study may be useful identifying persons who should be monitored most closely for the development of oral cancer and to recognize oral cancers at the earliest, most treatable stage. In the second study, NIDCR is collaborating with NCI on a study of oral, pharyngeal, or laryngeal cancer. The purpose of the study is to identify determinants of early vs. late stage of oral cancer at diagnosis; determinants of of patterns of treatment and rehabilitation; and the effects of comorbidities on mortality. The population includes 30,000 persons 65 years of age and older derived from a database that combines the Medicare statistical system and a data system containing information on cancer cases diagnosed and reported in nine geographically distinct population-based tumor registries. The principle purpose of the third study is to identify sociodemographic, behavioral, nutritional, dental, and genetic risk factors for oral and pharynx cancers in Puerto Rico. The genetic factors include genotypes that are involved in the metabolism of carcinogens. This large, population-based case-control study provides insights into the etiology of oral and pharyngeal cancer and the reasons for the high incidence rates of these cancers in Puerto Rico.